Arginine-, hypoxanthine-, uracil-requiring isolates of Neisseria gonorrhoeae are a clonal lineage within a non-clonal population

Abstract

Multilocus enzyme electrophoresis has shown that a collection of I 0 1 arginine-, hypoxanthine-, uracil-requiring (AHU') isolates of Neisseria gonorrhoeae, recovered over a 39 year period from the UK and Denmark, were of a single electrophoretic type (91 O/ O of strains), or differed from the predominant electrophoretic type at only a single locus. The striking uniformity of the AHU' isolates, and the correlation between auxotype, serovar and overall genetic background, contrasts with previous studies of gonococcal populations (that included very few AHU' strains), and a small sample of non-AHU' isolates studied here, which demonstrated a non-clonal population structure and a lack of association between auxotype, serovar and genetic background. There was no marked difference in the ability of AHU' isolates to be transformed with their own DNA, or with DNA from gonococci of other auxotypes, and the relative genetic stability of AHU' isolates does not appear to be due to a defect in their ability to be transformed. An alternative possibility is that AHU' gonococci recombine with other lineages, but that the resulting recombinants are not maintained in the population. This would occur, for example, if AHU' gonococci competed poorly in mixed infections, within which effective recombination between lineages occurs, and are usually only transmitted from individuals who are singly infected with an AHU' strain. The association between AHU' gonococci and asymptomatic infections may lead to an increased rate of transmission of these strains which under this scenario would be needed to prevent them from being lost from the population.

Review and International Recommendation of Methods for Typing Neisseria gonorrhoeae Isolates and Their Implications for Improved Knowledge of Gonococcal Epidemiology, Treatment, and Biology

“…Multilocus sequence typing (MLST) was first developed and implemented for differentiating Neisseria meningitidis isolates (89) as a general approach for molecular epidemiology and genetic analysis of strain populations. The method is a molecular extension of multilocus enzyme electrophoresis (MLEE) (28,29,61,110,134,143), in which electrophoretic mobilities of housekeeping enzymes are analyzed on starch gels. In MLST, the DNA sequences of internal fragments of the alleles of seven or more chromosomal housekeeping genes, which are relatively conserved, slowly evolving, evolutionarily more neutral, and, ideally, distributed throughout the genome, are analyzed.…”

por Variable-Region Typing by DNA Probe Hybridization Is Broadly Applicable to Epidemiologic Studies of Neisseria gonorrhoeae

“…Although N. gonorrhoeae has been described as a panmictic organism, clonal outbreaks have been described in association with disease presentation (16,18) or antibiotic resistance (47). Within defined temporal periods and geographic regions, isolate typing can be used to examine transmission patterns, disease clusters, and antibiotic resistance outbreaks.…”

Detection of mixed infection of Neisseria gonorrhoeae

“…M ixed gonococcal infection, where an individual is colonised simultaneously with more than one strain in the same anatomical site, is reported to occur frequently, particularly in highly sexually active populations [1][2][3][4] ; however, there is not a strong evidence base. When more than one strain occurs together, in vivo, it is hypothesised that lysis of the bacteria will occur, releasing DNA, which acts as the source for recombination resulting in a highly genetically variable population.…”